1. Field of the Invention
This invention relates to an electrochemical method for producing a 1,4-dihydro aromatic hydrocarbon with ammonia as the anode depolarizer and with improved long-term current efficiency.
2. Discussion of the Prior Art
U.S. Pat. No. 3,699,020 discloses a process for the production of a 1,4-dihydro aromatic hydrocarbon compound comprising electrochemically reducing at a cathode an aromatic hydrocarbon compound contained in an organic solvent-electrolyte system, introducing ammonia into this system, and concurrently oxidizing ammonia at an anode.
Experimentation subsequent to the filing of the application for U.S. Pat. No. 3,699,020 has indicated that, although operative, the method of U.S. Pat. No. 3,699,020 is often characterized by continuously declining current efficiencies, when a large extent of cathode reaction occurs, that is in electrolyses of relatively long duration and with relatively large current densities. For example, under the conditions of Examples I and II in U.S. Pat. No. 3,699,020, the current efficiency for the production of the 1,4-dihydro product ultimately declined to zero in electrolyses of long duration, and it was necessary to disassemble the cell and clean the cathode with sandpaper in order to regenerate high current efficiency for the production of the 1,4-dihydro product. Such effects were not originally detected in Examples I and II of U.S. Pat. No. 3,699,020 because the electrolyses therein were of short duration.